History of present illness
A 61-year-old man was referred to the department of pulmonary medicine because he had worsening shortness of breath. Chest radiograph showed ground-glass and reticular shadows in both lower lung fields with decreased lung volumes ( Fig. 6.1 ), suggesting a diagnosis of interstitial pneumonia.
Past medical history
The patient was an office worker and had no exposure to dust or inhaled toxins. He smoked about 20 cigarettes/day for 41 years, until he was age 59. However, he continued to be exposed to passive smoke. His family history was negative for interstitial lung diseases. His residence was a 25-year-old wooden house with good sunlight and no mold. He usually wore a down jacket in winter. He has a history of pneumonia and pleurisy at the age of 45. Five years before the current evaluation, he was found to have a chest radiographic abnormality; he was diagnosed with chronic obstructive pulmonary disease and emphysema, and his family doctor prescribed bronchodilators.
Physical examination and early clinical findings
At his first presentation, the patient had dyspnea with a Modified Medical Research Council (mMRC) score of 2. Oxygen saturation measured by the pulse oximetry (SpO 2 ) was 95% at rest in room air. Physical examination revealed mild fine crackles on both sides of the back. There were no physical findings suggestive of collagen vascular diseases such as Raynaud phenomenon, arthralgia, skin rash, myalgia, or muscle weakness. Chest computed tomography scan showed bilateral, lower lobe, basal predominant ground-glass shadows around cysts ( Fig. 6.2 ). There was also swelling of the mediastinal lymph nodes, especially below the tracheal bifurcation ( Fig. 6.3 ).
Blood tests showed a mild increase of KL-6 (696 U/mL, reference value < 500 mL), angiotensin-converting enzyme (ACE: 30.5 IU/L, reference value 7.7–29.4 IU/L), IgG4 (134 mg/dL, reference value 4.5–117 mg/dL), and IgE (500 mg/dL, reference value < 170 mg/dL), but soluble interleukin (IL)-2 receptor was within normal range, and all autoantibodies for collagen vascular disease were negative. Pulmonary function tests showed restrictive ventilatory impairment and decreased diffusion capacity as follows: forced expiratory volume in 1 second (FEV 1 )/forced vital capacity (FVC) 75.7%, vital capacity (VC) 2.63 L (64.3% predicted), FVC 2.71 L (68.1% predicted), and diffusing capacity of the lungs for carbon monoxide (DLCO) 45.2% predicted. Arterial blood gas analysis showed pH 7.40, PaO 2 83.9 mmHg, PaCO 2 40.4 mmHg, and HCO 3 – 24.5 mEq/L (room air, supine). In the 6-minute walk test, he covered a distance of 420 m, but the SpO 2 decreased to a minimum of 91%.
Clinical course
Based on clinical and imaging findings, idiopathic interstitial pneumonia, collagen vascular disease–related interstitial pneumonia, and sarcoidosis and IgG4-related diseases were listed as differential diagnoses. Bronchoalveolar lavage (BAL; right B4) showed a recovery rate of 94/150 mL, and cell fractions were macrophages 86%, lymphocytes 10%, eosinophils 2%, and neutrophils 2%. Transbronchial lung biopsy (TBLB) in the S8 segment of the right lower lung lobe and transbronchial needle aspiration (TBNA) from the subcarinal lymph nodes showed no specific findings.
Surgical lung biopsy and mediastinal lymph node biopsy were performed for further investigation, which revealed aggregates of pigmented macrophages in the alveolar space with thickening of the alveolar wall ( Fig. 6.4 ). There were scattered lymphoid follicles; IgG4 staining showed no significant increase in IgG4-positive cells. Histological examination of the lymph nodes showed nonspecific findings with no granulomas and no significant increase in IgG4-positive cells.
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